When the 'Limit' light flashes.....

[fusionbassist1]

Morning all.

I've been gigging for some considerable few years now for my age but have only recently broke into decent amp setups. (Bear with me, a short story)

When i first wanted a big amp i though "start at the bottom of the pile" so I got a Behringer BX4500 (gasp) with one of their 1x15" speakers. I found with certain eq's dialed the pretty red light underneath the word 'limit' would flash with the master volume around half way. I normally take red flashing lights as an omen of bad things to come so I'd have to back off the volume and try to get the drummer to quiet down.

I now have a (now discontinued) Portabass PB800 going into a GK Neo212. The limit light, without fail WILL light up if i exceed half way on the master volume knob.

On a similar thread I've also had an Ampeg V4B. Granted this is an all valve head with around 100Watts of beef but I laso found past half way with this amp to be a distortion nightmare.

I don't play in very loud bands but both the solid state amps I've described pump out around 300watts at 80hms which should be mroe than enough shouldn't it?

What with there being so much manipulation of figures when it comes to handling power, RMS etc I've just resorted to using my ears. But when an amp starts 'limiting' and flashing I get worried. My understanding of limiting is from an amateur engineers point of view - Where a compressed signal is pushed up to as close to 'very loud' (0db?) as possible during the mastering process and when i think of that in a gigging situation it doesn't sound like a desirable process to take place.

Could someone please clear up my worries as I'd like not to destroy an amp or speaker any time soon.

thanks a lot guys 'n' galls.

Ben.

P.S. I think I'm going to hop over to the introduction page as I never filed a 'hello everyone' post and I think it's about time i did so.

[Machines]

Sounds like you're overloading the preamp - try turning the gain(input) down or have a flatter EQ with less boost. Also if you have an active bass make sure it's going into the active input..

[bass_ferret]

According to the [url="http://www.ampeg.com/pdf/PB800.pdf"]manual[/url] it wont do any harm. Position on the master is irrelevant but it does suggest you are giving it full beans. I tried the PB250 when they first became available and my whelm has never been so under. I lit up the clip light in the shop IIRC.

So you either need another cab or a more efficient cab to get more volume. As the GK Neo 212 is 101dB you are gonna struggle to get a lot more efficient cab.

Edited August 7, 2008 by bass_ferret

[fusionbassist1]

I always set the gain perfectly, so that I can really wack a string hard with the peak light just about coming on. Passive bass, in the passive input.

I'm hopefully going to get another matching cab to get 550watts @ 4ohms out of the head. That should be enough headroom.

The symptoms I describe suggest that the top half of the master volume knob are redundant until you've got a cab setup that is at an impedance to get the full wack out of your bass head ie 2ohms mroe often than not.
correct?

[bass_ferret]

No. The top half of your master is redundant because your amp is hitting the limiter; because the combination of input voltage + preamp and power amp have reached the threshold of the limiter. Yes you will get more watts out of the amp by adding another cab but the real gain is adding another cab usually increases the SPL by 3dB because you are moving more air. Adding another cab probably wont let you turn the master up but it will mean that it will be louder at that setting and you can probably reduce the master so the limiter threshold wont be hit.

This is a different thing to setting the pre-amp gain to the appropriate level using the peak light. This is done to get the best signal to noise ratio. Some of this is explained on the basschat wiki.

[alexclaber]

[quote name='fusionbassist1' post='257650' date='Aug 7 2008, 10:32 PM']I'm hopefully going to get another matching cab to get 550watts @ 4ohms out of the head. That should be enough headroom.[/quote]

It probably won't be enough headroom to avoid ever running out of it but it will reduce the frequency of hitting the limiter or clipping. It's almost impossible to have enough headroom to never clip an amp unless you have immense power and lots of speakers or you compress/limit your bass sound. Generally I wouldn't worry about clipping lights unless they are associated with bad noises. Bad noises mean turn down, anything else is usually ok. Adding the extra cab will make more difference than lowering the load to 4 ohms.

The reason master volume knobs usually cause distortion when turned beyond halfway is because of so many bassists saying "I never need to turn my amp beyond 3" to show how load their amp is. They neglect to mention that turning it beyond 5 causes distortion. My amp rig doesn't sound terribly loud at 'normal' settings - but you can turn it up and up and up!

Alex

[Finbar]

My ampeg pre has the limit light flashing on just about every note I hit, even with the gain knob pretty much all the way down. I tame the signal with the master volume and the power amp volume knob, so I've never had sound issues from it.

I haven't broken it yet.

Don't worry about it. If it clips, big deal. If it clips and *sounds bad* then you might need to address it.

[peted]

Does anyone else find the active/passive input a bit of a misnomer? I much prefer amps which refer to it as 'padding' as I have a passive bass which has a hotter output than my active basses. I would suggest one, or a combination of the following and see if they have an effect on the limit light:

1) Plug your passive bass into the active input, you might have a really hot output passive bass
2) Use any EQ on your amp to cut frequencies rather than boost them (if they center at 0, leaving the preferred frequencies at 0 to stand out)
3) Start with the volume knob at 75% and all other dials at 0%. Check each dial in turn while playing to see where the culprit lays.